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  1. #11
    Bob F.'s Avatar
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    Quote Originally Posted by Donald Miller
    The second hypo bath (without Sodium Sulfite) is saved for the next printing session and becomes the first fixing bath by the addition of Sodium Sulfite and a new hypo bath (Sodium Thiosulfate) is prepared for the second bath.

    If you will follow this procedure, I will imagine the staining you note will be eliminated.
    That makes sense: the second fixer bath is alkaline (prevents acid carry over) and ensures full fixing (unless you get really sloppy) - both of which cause staining. I have resisted the use of two fixer baths before now - I think that explanation from Donald has switched me over to using them as rather than being too much hassle, it will actually save time when using selenium...

  2. #12

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    I am no chemist and can't tell you what each and every ingredient accomplishes in fixer. For that reason, I wouldn't disagree with what Don has posted.

    It does, however, differ from what I have learned in reading AA's book and in attending several of John Sexton's seminars. John follows Ansel's working methods in fixing and toning.

    He uses the Kodak F6 formula for fixer - reducing the amount of alum by 1/2. (Alum is an agent that hardens the emulsion.) The reduced alum aids toning.

    The second fixing bath is sodium thiosulfate dissolved in the concentration of 1/2 pound per gallon of water plus 1/4 pound of sodium sulfite per gallon. This differs from the F6 formula in that it contains no alum, no acetic acid and no kodalk (sodium metaborate).

    I use their process and have never had a problem with staining.

  3. #13
    Ole
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    Hmmm...

    The first fixer would do most of the fixing, and a bit of hardening.

    Then the second fixer is a very weak alkaline fixer, which leaches out the remaining silver salts, softens the emulsion, and neutralises the alum.

    So why use hardener at all, or indeed acid fix?
    -- Ole Tjugen, Luddite Elitist
    Norway

  4. #14
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    For many years I have made working solution of Se Toner by adding 1/4-teaspoon (heaping) Kodalk to 64-oz. of Selenium solution of whatever ratio I happened to choose (in other words, with water; no hypo-clear).

  5. #15
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    Quote Originally Posted by Ole
    Kodak Rapid Selenium Toner - KRST - contains ammonium thiosulfate, and quite a lot of it too!
    Per the MSDS, 27% by weight.
    Quote Originally Posted by Ole
    I don't know why, but ammonium thiosulfate is a strong enough silver solvent that I can imagine it will speed up the toning process considerably.
    The presence of thiosulfate does appreciably speed up the toning process (hence the Rapid in the name). I haven't found the definitive answer yet, but as mentioned above, thiosulfate is a silver solvent and will, in high enough concentration and/or after enough time, dissolve part of the silver in the image. This solvent action may, by increasing the number of silver ions present in the solution, speed up the formation of the silver selenide that provides the image color.

  6. #16

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    Quote Originally Posted by Ole
    The first fixer would do most of the fixing, and a bit of hardening.
    Then the second fixer is a very weak alkaline fixer which leaches out
    the remaining silver salts, softens the emulsion, and neutralises
    the alum. So why use hardener at all, or indeed acid fix?
    I've read that page on Adams' process routine. I tried to find that
    page a few months ago but think it has been deleted.

    After stop and first fix he used a holding bath. I can imagine that
    prints were held for hours prior to seeing the second fix. Sixty years
    ago, papers I believe, were not so prehardened as today. Like it
    or not, most if not all today's papers have incorporated
    hardeners. That is my understanding. Dan

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